I was out riding today and it was running great. Went through a big puddle and tipped over. Airbox didnt submerge but a little water went in. I checked it when I got home and there was 2 drops in the boot but that couldve been from when I took the filter off. But before this I noticed a very quiet whine/whistle when the revs were coming down and there was no real engine noise. I thought ok, it's probably intake no big deal, but through out the day it got louder and then on decel it started to rattle real bad, probaly around 4000RPM. No rattle on the low end or top end just in the middle and only coming down on revs. The rattle is really loud and noticable. I first though a bolt or something in my powervalve came loose and that's what was rattling, but I didn't lose any top end power so the valve was opening properly. I couldn't get the right hand cover off because of the pipe and tank. I took the left off and we revved it but not high enough to make the powervalve move I think. I talked to a guy while I was waiting for a guy home and he said to him it sounded like piston slap. It's definately due for a top end but it was pretty sudden. I had it out a few times previously with no noise at all, now this bad rattle.